Untransfected MCF-7 cells undergo cell death following treatment with recombinant TNF-α. (A) MCF-7 cells were treated with 100 ng/ml TNF-α, and cell viability was assessed using the MTT assay. Absorbance values are expressed as a percentage of those in non-treated control samples at each timepoint. Error bars are derived from triplicate wells of one representative experiment. (B) Flow cytometry analysis of untreated or TNF-α-treated MCF-7 cells. Cells were trypsinized, fixed in ethanol, and incubated with propidium iodide prior to analysis by flow cytometry. 10,000 cells were counted for each condition. Data are expressed as the percentage of cells containing sub-2n DNA content in one representative experiment.